Pneumatic spring structures



- container.

United States Patent C) P Ice Patented Mar. 14, 1961 This inventionrelates to the control of pneumatic spring structures, for example forvehicles, in which the spring force is produced by the elasticcompression of a gas cushion yand is variable, the gas pressure beingsuited to the vehicle load and/ or to the state of the road. ControlsareV known in which gas can be discharged from the gas cushion through avalve into the open air, whereby the spring force is reduced, andgas canbe yadmitted from a compressor or from a pressure bottle, whereby thekspring `force is increased. These` controlsr have the disadvantage thatthe discharged gas itself and the energy contained in this gas whilestill compressed are completely lost. Also a compressor, for example,when air is used for springing,rnustovercome the whole pressurediiierence between the atmospheric pressure and the pressure in thecushion.

The control according to the invention is characterised by the gascushion being connected through valves or other control members to twogas containers which are connected together through a compressor, ofwhich one, the lower pressure container, is lled with gas at a lowerpressure than the operating pressure of the gas cushion and the other,the higher pressure container, with gas at a higher pressure than theoperating pressure of the cushion. If the pressure of the gas cushion isto be reduced, gas is discharged into the lower pressure container. Thenonly the energy corresponding to the pressure drop from the gas cushionto the container is lost. If the pressure of the gas cushion is to beraised, gas is admitted to it from the higher pressure container.

The compressor between the lower pressure and higher pressure containersnow only has to overcome the small pressure difference between these twocontainers. With the existence of the containers, in particular a higherpressure container, the advantage is at the same time -obtained that theadmission of gas into the cushion canv take place very rapidly, in anycase more rapidly than if the compressor had to supply gas directly tothe cushion without the interposition of a gas container.

In pneumatic spring structures in which the gas cus'hi example, forhydraulic damping of Vibrations, it is advantageous to let the lowerpressure container and the higher presusre container also co-operatewith Volumes of oil and to connect all the oil volumes together throughvalves, in which case an oil pump may also be arranged between the lowpressure container and the high pressure container. In this way, it ispossible to reduce the volume of oil which is combined with the gascushion by discharging oil into the low pressure container or toincrease it by admitting oil from the high pressure In this way theVolume of the gas cushion can be varied and a desired alteration inspring characteristic be obtained. Also the volume of oil co-operatingwith the gas cushion can be rectified if there is a free surface betweenthe oil volume and the gas cushion,

.and upon discharge or admission of gas, oil may be car- .ried with thegas so that the oil volume changes.

The accompanying drawing is a diagrammatic sec-- tional view of anexample of a pneumatic spring struc' ture according to the inventionwhich co-operates with a volume of oil. c

A piston 1, having a piston rod 2, slides in a working cylinder 3 whichcontains a gas cushion 4r and an oil volume 5 separated by a freesurface 6. The piston 1 is provided with valves not shown of a knownkind which produce damping forces when the piston moves in Vthe workingcylinder. The free spring force corre-y sponds to the product of thepiston rod area and thel pressure of the gas cushion. The damping andspring forces are transmitted from the end of the piston rod 83 and abase part 9 of the working cylinder 3 to corresponding parts of avehicle. The piston rodis sealed in relation to the outside air by apacking 7.

The gas cushion 4 is in communication through a nonreturn valve 1li anda regulating valve 11 with a;

lower pressure container V12 and also through a non# with the oil space18 of the lower pressure container` through a non-return valve 22 and aregulator valve/23 and with the oil space 19 of the higher pressurecontainer through a non-return valve 24 and a regulating valve 25. Thefunction of the non-return valves 10 and 22 is to prevent the outllow ofgas or oil from the lower pressure container, if when the regulatingvalve 11 or 23 is open in consequence of the movements of the piston rodS, the pressure of the gas cushion 4 falls below the pressure within thelower pressure container. Similarly, the non-return valves 13 and 24prevent the return of gas or oil into the higher pressure container whenthe valves 14 and 25 are open, if the pressure of the gas cushion shouldrise above the pressure in the higher pressure container, due to themovements of the piston rod 8.

The lower pressure container and higher pressure container are connectedby pipes 26 and 27 in which are incorporated respectively a compressordiagrammatically i indicated at 28 and pump diagrammatically indicatedat 29, by which means the desired pressure difference bewith said gascushion, a lower pressure container having a gas space communicatingwith said gas cushion, a volume of oil,in said lower pressure container,a higher pressure container having a gas space communicating with saidgas cushion, a volume of oil in said higher pressure container,connections between the volume of oil in said containers with the volumeof oil co-operating with the gas cushion, means for regulating the flowof gas between said cushion and said containers, means for regulatingthe flow of oil between the oil co-operating with the gas cushion andthat in the containers, a com-V pressor connecting the gas space of saidlower pressure container with the gas space of said higher pressurecontainer, and an oil pump connecting the oil in said lower pressurecontainer with the oil in said higher pressure container.

2. A pneumatic spring structure as set forth in claim 1 wherein said gascushion 'is constituted by a gas filling in a working cylinder whichalso contains the volume of oil co-operating with the gas cushion, saidcylinder having a piston working therein immersed in the oil and havingvalves in the piston whereby movements of the piston are hydraulicallydamped, said piston being attached to a rod projecting out of saidcylinder and said cylinder and piston rod constituting the -anchoragesof the spring structure.

i 3. A pneumatic spring structure as set forth in claim l alsocomprising non-return valves which prevent backow of gas or oil fromsaid lower pressure container to said gas cushion or the oil volumeco-operating therewith and preventing backow of gas or oil from said gascushion or the volume of oil co-operating therewith to said higherpressure container.

4. A liquid pneumatic suspension systemfor vehicles, of the type whichis variable in accordance with vehicle conditions, comprising incombination a cylinder having an oil volume and a gas cushion atelevated pressure above ambient, a piston in said cylinder forconnection to a part of the vehicle, a lirst pressure container havingan oil volume and a gas volume at elevated pressure 4 umes of the saidfirst and second pressure containers and an oil pump connected betweenthe respective oil volumes of the said first and second pressurecontainers. 6. A pneumatic spring structure for vehicles comprising incombination, a gas cushion having a volume of oil and a volume of gasand variable pressure to suit external conditions such as loading orroad surface conditions, a lower pressure container having a volume ofoil and a volume of gas, a higher pressure container having a volume ofoil and a volume of gas, control means connecting the volume of gas ineach said container with the volume of gas in said gas cushion, a gascompressor connecting the respective volumes of gas in the saidcontainers whereby pressures higher and lower than the operatingpressures of the gas cushion are maintained respectively in the higherpressure container and the lower pressure container, and control meansconnecting the volume of oil in each said container with the volume ofoil in said gas cushion.

7. A pneumatic spring structure as set forth in claim 6, including anvoil pump connecting the respective volurnes of oil in the saidcontainers.

References Cited in the tile of this patent UNITED STATES PATENTS

